“In a challenge to the idea that brain death is final, researchers have revived the disembodied brains of pigs four hours after the animals were slaughtered. Although the experiments stopped short of restoring consciousness, they raise questions about the ethics of the approach — and, more fundamentally, about the nature of death itself. ”
—Sara Reardon, “Pig brains kept alive outside body for hours after death.” Nature. April 17, 2019.
Reminds me of a question I heard about whether anyone is still conscious during organ harvesting. The idea of being vivisected while conscious is serious nightmare fuel.
Brain in a vat has the potential to be worse because it could go on indefinitely, see Iain M. Banks Surface Detail as one possibility.